This is a prospective study of a cohort of injecting drug users in New Delhi, India. Injection of buprenorphine in the Indian sub-continent and adjacent countries has grown dramatically in recent years, promoting high levels of HIV incidence and severe drug-related health consequences. The study will examine efficacy of a 3-strategy intervention to reduce HIV and drug-associated risks, and will include (1) immediate access to a needle exchange program (NEP), health education and access to condoms, (2) voluntary counseling and testing for HIV-1 and diagnosis and treatment for sexually transmitted, Infections (STIs), and (3) drug treatment with oral substitution of buprenorphine. NEP, health education and condoms will be provided at enrollment after baseline assessment. HIV VCT and STI screening and treatment will occur 3-months later after a follow up assessment. Oral buprenorphine substitution will be provided at 6-months from baseline and following a 6-month assessment. Assessments of drug risks and health status will be conducted at 9- and 12- months, and participants will be tracked for enrollment in detoxification programs after drug treatment to assess cessation of drug use. The study will enroll 500 IDUs from a slum community in which preliminary studies and risk reduction interventions have been conducted. The study will evaluate the efficacy of each of the three interventions components, and will also include a detailed cost-effectiveness analysis. The intervention is theoretically based on preliminary data showing that 44 percent of study participants were HIV-1 infected, yet 33 percent know what HIV or AIDS is, and among them few had accurate knowledge of HIV. Risk behaviors among this population are extremely high, and evidence that NEP and oral buprenorphine substitution are effective at reducing risk behaviors for HIV and drug-related health outcomes among drug users. Moreover, HIV-1 VCT provided in the preliminary study appeared to result in significant reductions in risk, and was well accepted by injecting drug users. Thus, the intervention will first increase knowledge of HIV and associated risk behaviors, and attempt to immediately reduce risk behaviors and stabilize health problems. HIV VCT follows once knowledge deficits are corrected, and drug treatment will be provided after an adjustment period to the HIV test results. The study is being conducted in collaboration WI an Indian non-governmental organization which has many years of experience in providing services to slum communities and injecting drug users. Leading Indian scientists who have conducted clinical trials among drug users are collaborating on the project. The results of this project will be used to rigorously examine the effectiveness of interventions which could be (replicated in multiple-countries, and the cost-effectiveness component of the study will provide important information on the feasibility of replication of the intervention program, and how to maximize benefits through targeting approaches.